Documents such as identity cards as well as goods such as pharmaceutical products are items that need to be authenticated and tracked. There is a need to differentiate between authentic products and counterfeited ones. A thorough authentication can be performed by comparing the identifier of a document whose authenticity is to be verified with identifiers of original valid documents that have been issued. Similarly, the identifier of a good whose authenticity is to be verified should be compared with identifiers of the authentic goods. Identifiers of original documents or goods may be overt or covert.
In the present invention, the identifiers are encoded as spatial codes that are hidden within a halftone multigrating image reproduced on the document or good to be protected. Means are disclosed to hide a spatial code message within an apparently variable intensity or variable color image that is formed by the halftone of a line grating. The spatial code message is revealed by a smartphone acquiring with its camera an image of the region of a document or product where the spatial code is hidden and by digitally superposing onto the acquired image a corresponding matching digital revealing layer grating. Such a region may show a visible graphic element, a logo, a text, a face or any other grayscale, variable intensity or color image. The smartphone is connected through the Internet with an authentication and tracking computing server. This computing server verifies the authenticity of the acquired and decoded spatial code messages and sends an acknowledge message back to the smartphone having performed the acquisition. The computing server also tracks the corresponding documents or products by registering their identity as well as the smartphone identifier, date, time and geographic location of the corresponding image acquisition.
In nearly every industry branch, there is a need to track the products that are being sold. There is also a need to track user responses to advertisement campaigns. One may also use a similar tracking infrastructure to track persons that move within a given environment, for example the area of a production site.
Today's tracking systems rely mainly on messages incorporated into barcodes, data matrix codes, Aztec codes or QR-codes. These kinds of codes have the disadvantage of being directly visible to human beings and at the same time of being relatively ugly. There is a need of hiding these codes and the message that they carry about a product, a service or a person. For example, hiding such a code within a product label helps raising the acceptability of that product. As a further example, a personal pass containing information hidden within the face image of the document holder reinforces the security of that pass and at the same time increases its acceptability among the holders of these documents. The main advantage of the proposed system for hiding spatial codes resides in the fact that the spatial codes are not modifiable without knowing the parameters with which they were synthesized. Such non-modifiable hidden spatial codes offer a strong additional protection, compared with classical overt 1D or 2D barcodes.
The present disclosure describes an authentication and tracking system where these codes are used, but are hidden into grayscale, variable intensity or color images that have a significance for the human observer. For example, if a company wants to track its product, e.g. a camera, it may print a small label pasted onto the camera housing that shows the logo of the company, namely a camera diaphragm. Without being informed, persons looking at such a picture cannot guess that it hides a spatial code containing a message. When printed as a base layer multigrating image, the camera diaphragm may be photographed by a smartphone running the authentication and tracking software. The authentication and tracking software applies perspective correction, fine grain rectification, phase-controlled superposition of a matching revealing layer grating as well as image processing operations to extract the hidden spatial code, decode it and send it to the computing center of the company having produced the camera. In addition to the information decoded from the acquired image, the authentication and tracking software delivers useful information, such as the date, time and location where the picture was taken. The person holding the smartphone may then receive information telling him that this camera product is genuine and not a counterfeit. With hundreds of thousands of customers interested in buying such cameras, the company is then able to build a geographic map showing the location of its potential customers. It will also get information about the gray market, i.e. countries where these cameras are imported without authorization from the manufacturer.
U.S. patent application Ser. No. 11/149,017, now U.S. Pat. No. 7,305,105 filed Jun. 10, 2005, entitled “Authentication of secure items by shape level lines”, inventors Chosson and Hersch (also inventor in the present application), gives information useful to understand the present disclosure. Shape level line techniques have also been published in December 2014, see reference [Chosson and Hersch 2014] at the end of the present specification, incorporated herein by reference. Shape level line moirés occur in a superposition image when a base layer comprising a line grating locally shifted according to the elevation of a spatially laid out shape elevation profile is superposed with a revealing layer comprising the unshifted sampling line grating. The elevation profile is generated from an initial bilevel shape image. In previous works, the initial bilevel image could be formed by printed typographic characters, symbols, a logo, or an ornament. The superposition of a base layer printed on paper and of a revealing layer printed on a transparency yields the level-line moiré, which shows the level lines of the elevation profile. By modifying the relative superposition phase of the sampling revealing layer grating in superposition with the base layer (e.g. by a translation), one may observe as shape level line moiré successions of level lines of the shape elevation profile evolving dynamically between the initial motif shape boundaries and shape foreground centers, respectively shape background centers. In patent application Ser. No. 14/703,017, the printed base and revealing layer line gratings are replaced by arrays of cylindrical lenslets, which due to their interaction with incident light, show in transmission mode similar level-line motives as their printed counterparts.